K-25 Structural Separation and Demolition
- Bechtel Jacobs Company, LLC, East Tennessee Technology Park, Post Office Box 4699, Oak Ridge, TN 37831 (United States)
The K-25 building is a former gaseous diffusion plant, built in 1944-1945 as part of the United States Manhattan Project. The structure was the largest structure under one roof, surpassed only by the Pentagon. Together the three wings represent about 17.8 hectare (44 acres) under roof and are generally about 18.3 meters (60 ft.) high on the outside face and approximately 12.2 meters (40 ft.) high on the inside face. The entire structure was built in the shape of a 'U', with a lateral distance of approximately one mile. It was constructed in individual building units with each unit connected using expansion joint-type connection. A single unit is approximately 24.4 meters (80 ft.) across and 122 meters (400 ft.) deep. The northern structure is connected to the eastern and western structures at the upper level floors. The four-level, U-shaped building is a steel-frame structure with corrugated cement-asbestos siding. The cell level is an elevated concrete structure supported by reinforced concrete columns located in the basement, or vault area. The vault area can be accessed at grade level from the outside perimeter. Inside the courtyard, the grade level has been raised to provide entry to the second or cell floor level. An engineering evaluation of the structure was performed to determine the condition of the structure and possibility of unplanned collapse of any portion of the structure. The evaluation included physical inspections, calculations for wind, pre-demolition loads, and evaluation of failure modes. The results of the evaluation have provided guidance for the demolition plan and the development of criteria for protection of personnel performing pre-demolition activities. Challenges include degradation of the structure that necessitated repair, dealing with changes in the code revisions from both the American Concrete Institute (ACI) and the American Institute of Steel Construction (AISC), access to areas of the structure that were not necessarily designed for access, and acceleration of the building degradation due to the pre-demolition activities. When a full building is evaluated, 50 percent of wind and applied forces are dissipated in 3 units and 80 percent is dissipated in 12 units. The forces are basically linear for the first 6 units once the building is opened at the start of demolition. Some column buckling, based on current codes, was noted in the analysis that would have to be mitigated to ensure a controlled demolition. Loading for the removal of the equipment required structural engineering evaluation of the certainty of the load and the application of the load. Corbels are being evaluated through an inspection program and criteria for repair based on current loading and anticipated additional live loads. Access issues continue to be a challenge and have created the need for a significant fall protection program. Other areas of access require different approaches and engineering solutions, sometime considering ultimate strength design versus standard yield stress design. An evaluation of separating a wing into two sections to allow for worker re-entry to perform pre-demolition activities during the demolition off shift was conducted. The evaluation has shown that because of both design and history of the K-25 and K-27 Buildings, significant care and attention is needed to demolish these structures from a structural perspective. When the project schedule issues are overlaid, that may demand workers in other parts of the structure after demolition has begun, the structural issues become severe, demanding exacting analysis and significant controls to ensure the safety of the workers both in and outside the building performing the demolition work.
- Research Organization:
- American Nuclear Society, 555 North Kensington Avenue, La Grange Park, Illinois 60526 (United States)
- OSTI ID:
- 21144227
- Resource Relation:
- Conference: DD and R 2007: ANS Topical Meeting on Decommissioning, Decontamination, and Reutilization 2007, Chattanooga, TN (United States), 16-19 Sep 2007; Other Information: Country of input: France; Related Information: In: Proceedings of the 2007 ANS Topical Meeting on Decommissioning, Decontamination, and Reutilization - DD and R 2007, 336 pages.
- Country of Publication:
- United States
- Language:
- English
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